Air-conditioning apparatus

ABSTRACT

An indoor unit includes an air-sending fan, an air inlet through which air of an indoor space is sucked in, and an air outlet located above the air inlet and through which the air sucked in through the air inlet is blown out to the indoor space. A control unit activates the air-sending fan when leakage of the refrigerant is detected. When M [kg] represents an amount of charge of the refrigerant in a refrigeration cycle, LFL [kg/m 3 ] represents a lower flammable limit of the refrigerant, A [m 2 ] represents a floor area of the indoor space, and Ho [m] represents a height of the air outlet above a floor surface of the indoor space, the amount of charge M, the lower flammable limit LFL, the floor area A, and the height Ho satisfy a relationship of M&lt;LFL×A×Ho.

TECHNICAL FIELD

The present invention relates to an air-conditioning apparatus.

BACKGROUND ART

HFC refrigerants such as R-410A, which are non-flammable, areconventionally used for air-conditioning apparatuses. Unlikeconventional HCFC refrigerants such as R-22, R-410A has a zero ozonedepletion potential (to be referred to as “ODP” hereinafter), and hencedoes not deplete the ozone layer. However, R-410A has a high globalwarming potential (to be referred to as “GWP” hereinafter). Thus, aspart of global warming prevention measures, studies are under way for aswitch from HFC refrigerants with high GWPs, such as R-410A, torefrigerants with low GWPs.

Candidates for such refrigerants with low GWPs include HC refrigerantssuch as R-290 (C₃H₈, propane) and R-1270 (C₃H₆, propylene), which arenatural refrigerants. However, unlike R-410A, which is non-flammable,refrigerants such as R-290 and R-1270 have high flammability (highlyflammable). Thus, when R-290 or R-1270 is to be used as a refrigerant,care needs to be taken against refrigerant leaks.

Alternative candidates for refrigerants with low GWPs include HFCrefrigerants with no carbon double bond in their composition, forexample, R-32 (CH₂F₂, difluoromethane) with a GWP lower than that ofR-410A.

Similar candidates for such refrigerants include halogenatedhydrocarbons, which are a type of HFC refrigerants like R-32 and havecarbon double bonds in their composition. Examples of such halogenatedhydrocarbons include HFO-1234yf (CF₃CF=CH₂, tetrafluoropropene) andHFO-1234ze (CF₃—CH═CHF). HFC refrigerants with carbon double bonds intheir composition are often expressed as “HFO” using “O” for olefin(unsaturated hydrocarbons with carbon double bonds are called olefin) todifferentiate such HFC refrigerants from HFC refrigerants with no carbondouble bond in their composition, such as R-32.

Although such HFC refrigerants (including HFO refrigerants) with lowGWPs are not as highly flammable as HC refrigerants such as R-290, whichis a natural refrigerant, unlike R-410A, which is non-flammable, theseHFC refrigerants have mild flammability (mildly flammable). Thus, aswith R-290, care needs to be taken against refrigerant leaks.Hereinafter, refrigerants with levels of flammability equal to or higherthan mild flammability (for example, 2 L or higher in the ASHRAE-34classification) will be referred to as “flammable refrigerants”.

Leakage of flammable refrigerant into the indoor space causes indoorrefrigerant concentration to increase, potentially leading to formationof a flammable concentration region.

Patent Literature 1 describes an air-conditioning apparatus usingflammable refrigerant. The air-conditioning apparatus includes arefrigerant detection unit disposed on the outer surface of the indoorunit to detect flammable refrigerant, and a control unit that rotates anindoor-unit air-sending fan when the refrigerant detection unit detectsrefrigerant. In the air-conditioning apparatus, in situations such aswhen flammable refrigerant leaks into the indoor space from an extensionpipe leading to the indoor unit, and when flammable refrigerant that hasleaked out inside the indoor unit flows to the outside of the indoorunit through a gap in the housing of the indoor unit, the leakedrefrigerant can be detected by the refrigerant detection unit. Further,when a refrigerant leak is detected, the indoor-unit air-sending fan isrotated. As a result, the indoor air is sucked in from the air inletprovided in the housing of the indoor unit, and air is blown out intothe indoor space from the air outlet, thus enabling effective dispersionof the leaked refrigerant.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent No. 4599699

SUMMARY OF INVENTION Technical Problem

However, the amount of refrigerant charge is not specified for theair-conditioning apparatus described in Patent Literature 1. Thus, ifthe amount of refrigerant charge is excessive, a flammable concentrationregion can form in the indoor space even when the leaked refrigerant andthe indoor air are stirred by using the indoor-unit air-sending fan.

The present invention has been made to address the above-mentionedproblem, and an object of the invention is to provide anair-conditioning apparatus that reduces formation of a flammableconcentration region in the indoor space even when flammable refrigerantleaks accidentally.

Solution to Problem

An air-conditioning apparatus according to an embodiment of the presentinvention includes a refrigeration cycle through which refrigerant iscirculated, an indoor unit that accommodates at least an indoor heatexchanger of the refrigeration cycle, the indoor unit being disposed inan indoor space, and a control unit that controls the indoor unit. Therefrigerant is a flammable refrigerant with a density greater than adensity of air under atmospheric pressure. The indoor unit includes anair-sending fan, an air inlet through which air of the indoor space issucked in, and an air outlet located above the air inlet and throughwhich the air sucked in through the air inlet is blown out to the indoorspace. The air outlet is provided on a front face or a side face of ahousing of the indoor unit. The control unit activates the air-sendingfan when leakage of the refrigerant is detected. When M [kg] representsan amount of charge of the refrigerant in the refrigeration cycle, LFL[kg/m³] represents a lower flammable limit of the refrigerant, A [m²]represents a floor area of the indoor space, and Ho [m] represents aheight of the air outlet above a floor surface of the indoor space, theamount of charge M, the lower flammable limit LFL, the floor area A, andthe height Ho satisfy a relationship of M<LFL×A×Ho.

An air-conditioning apparatus according to an embodiment of the presentinvention includes a refrigeration cycle through which refrigerant iscirculated, an indoor unit that accommodates at least an indoor heatexchanger of the refrigeration cycle, the indoor unit being disposed inan indoor space, and a control unit that controls the indoor unit. Therefrigerant is a flammable refrigerant with a density greater than adensity of air under atmospheric pressure. The indoor unit includes anair-sending fan, an air inlet through which air of the indoor space issucked in, an air outlet located above the air inlet and through whichthe air sucked in through the air inlet is blown out to the indoorspace, and a vertical air deflector vane located at the air outlet. Theair outlet is provided on a front face or a side face of a housing ofthe indoor unit. When M [kg] represents an amount of charge of therefrigerant in the refrigeration cycle, LFL [kg/m³] represents a lowerflammable limit of the refrigerant, A [m²] represents a floor area ofthe indoor space, and Ho [m] represents a height of the air outlet abovea floor surface of the indoor space, the amount of charge M, the lowerflammable limit LFL, the floor area A, and the height Ho satisfy arelationship of M≧LFL×A×Ho. The control unit activates the air-sendingfan and sets the vertical air deflector vane to an upward orientationwhen leakage of the refrigerant is detected.

Advantageous Effects of Invention

The embodiment of the present invention reduces formation of a flammableconcentration region in the indoor space even when flammable refrigerantleaks accidentally.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit diagram illustrating the generalconfiguration of an air-conditioning apparatus according to Embodiment 1of the present invention.

FIG. 2 is a front view illustrating the exterior configuration of anindoor unit 1 of the air-conditioning apparatus according to Embodiment1 of the present invention.

FIG. 3 is a front view schematically illustrating the internal structureof the indoor unit 1 of the air-conditioning apparatus according toEmbodiment 1 of the present invention.

FIG. 4 is a side view schematically illustrating the internal structureof the indoor unit 1 of the air-conditioning apparatus according toEmbodiment 1 of the present invention,

FIG. 5 is a flowchart illustrating an example of a refrigerant leakdetection process executed by a control unit 30 in the air-conditioningapparatus according to Embodiment 1 of the present invention,

FIG. 6 illustrates the state of an indoor space 120 after operation ofan indoor air-sending fan 7 f is started through the process of step S3illustrated in FIG. 5 in the air-conditioning apparatus according toEmbodiment 1 of the present invention.

FIG. 7 is a plan view illustrating the configuration of the indoor space120 used in an experiment related to Embodiment 1 of the presentinvention.

FIG. 8 is a graph illustrating changes in refrigerant concentration overtime in a first experiment related to Embodiment 1 of the presentinvention.

FIG. 9 is a graph illustrating changes in refrigerant concentration overtime in a second experiment related to Embodiment 1 of the presentinvention.

FIG. 10 is a cross-sectional view illustrating the configuration in thevicinity area of an air outlet 113 of the indoor unit 1 of anair-conditioning apparatus according to Embodiment 2 of the presentinvention,

FIG. 11 is a flowchart illustrating an example of a refrigerant leakagedetection process executed by the control unit 30 in theair-conditioning apparatus according to Embodiment 2 of the presentinvention.

FIG. 12 illustrates the state of the indoor space 120 after operation ofthe indoor air-sending fan 7 f is started through the process of stepS14 illustrated in FIG. 11 in the air-conditioning apparatus accordingto Embodiment 2 of the present invention.

FIG. 13 illustrates an example of items written in the catalog of theair-conditioning apparatus according to Embodiment 1 of the presentinvention.

FIG. 14 illustrates an example of items written in the catalog orinstallation manual of the air-conditioning apparatus according toEmbodiment 1 of the present invention.

DESCRIPTION OF EMBODIMENTS Embodiment 1

An air-conditioning apparatus according to Embodiment 1 of the presentinvention will be described. FIG. 1 is a refrigerant circuit diagramillustrating the general configuration of the air-conditioning apparatusaccording to Embodiment 1. In the drawings including FIG. 1, featuressuch as the relative sizes of components and their shapes may not be toscale.

As illustrated in FIG. 1, the air-conditioning apparatus has arefrigeration cycle 40 through which refrigerant is circulated. Therefrigeration cycle 40 includes a compressor 3, a refrigerant flowswitching device 4, an outdoor heat exchanger 5 (heat source-side heatexchanger), a pressure reducing device 6, and an indoor heat exchanger 7(load-side heat exchanger) that are annularly connected in the statedorder by pipes. The air-conditioning apparatus further includes anindoor unit 1 that is installed indoors, for example, and an outdoorunit 2 that is installed outdoors, for example. The indoor unit 1 andthe outdoor unit 2 are connected to each other by extension pipes 10 aand 10 b constituting part of refrigerant pipes.

Examples of refrigerant circulated through the refrigeration cycle 40include a mildly flammable refrigerant such as R-32, HPO-1234yf, andHFO-1234ze, and a highly flammable refrigerant such as R-290 and R-1270.Each of these refrigerants may be used as a single-componentrefrigerant, or may be used as a refrigerant mixture that is a mixtureof two or more types of refrigerant. Each of these refrigerants has adensity greater than the density of air under atmospheric pressure (forexample, at room temperature (25 degrees C.)).

The compressor 3 is a piece of fluid machinery that compresseslow-pressure refrigerant sucked into the compressor 3, and dischargesthe compressed refrigerant as high-pressure refrigerant. Examples of thecompressor 3 used include an inverter-driven hermetic electriccompressor with adjustable rotation speed. The refrigerant flowswitching device 4 switches the directions of refrigerant flow in therefrigeration cycle 40 between cooling operation and heating operation.The refrigerant flow switching device 4 used is, for example, a four-wayvalve. The outdoor heat exchanger 5 is a heat exchanger that acts as aradiator (for example, condenser) in cooling operation, and acts as anevaporator in heating operation. In the outdoor heat exchanger 5, heatis exchanged between the refrigerant circulated in the outdoor heatexchanger 5, and the air (outside air) sent by an outdoor air-sendingfan 5 f described later. The pressure reducing device 6 reduces thepressure of high-pressure refrigerant to turn the refrigerant intolow-pressure refrigerant. The pressure reducing device 6 used is, forexample, an electronic expansion valve with an adjustable openingdegree. The indoor heat exchanger 7 is a heat exchanger that acts as anevaporator in cooling operation, and acts as a radiator (for example,condenser) in heating operation. In the indoor heat exchanger 7, heat isexchanged between the refrigerant circulated in the indoor heatexchanger 7, and the air sent by an indoor air-sending fan 7 f describedlater. The term cooling operation refers to an operation in whichlow-temperature, low-pressure refrigerant is supplied to the indoor heatexchanger 7, and heating operation refers to an operation in whichhigh-temperature, high-pressure refrigerant is supplied to the indoorheat exchanger 7.

The compressor 3, the refrigerant flow switching device 4, the outdoorheat exchanger 5, and the pressure reducing device 6 are accommodated inthe outdoor unit 2. Further, the outdoor air-sending fan 5 f forsupplying outside air to the outdoor heat exchanger 5 is alsoaccommodated in the outdoor unit 2. The outdoor air-sending fan 5 f isplaced opposite to the outdoor heat exchanger 5. Rotating the outdoorair-sending fan 5 f creates a flow of air that passes through theoutdoor heat exchanger 5. The outdoor air-sending fan 5 f used is, forexample, a propeller fan. The outdoor air-sending fan 5 f is disposeddownstream of the outdoor heat exchanger 5, for example, in thedirection of the flow of air created by the outdoor air-sending fan 5 f.

Refrigerant pipes disposed in the outdoor unit 2 include a refrigerantpipe that connects an extension-pipe connection valve 13 a located onthe gas side (in cooling operation) with the refrigerant flow switchingdevice 4, a suction pipe 11 connected to the suction side of thecompressor 3, a discharge pipe 12 connected to the discharge side of thecompressor 3, a refrigerant pipe that connects the refrigerant flowswitching device 4 with the outdoor heat exchanger 5, a refrigerant pipethat connects the outdoor heat exchanger 5 with the pressure reducingdevice 6, and a refrigerant pipe that connects the pressure reducingdevice 6 with an extension-pipe connection valve 13 b located on theliquid side (in cooling operation). The extension-pipe connection valve13 a is implemented as a two-way valve capable of being switched openand close, with a flare coupling attached at its one end. Theextension-pipe connection valve 13 b is implemented as a three-way valvecapable of being switched open and close. A service port 14 a that isused during vacuuming (during an operation performed prior to fillingthe refrigeration cycle 40 with refrigerant) is attached at one end ofthe extension-pipe connection valve 13 b, and a flare coupling isattached at another end.

High-temperature, high-pressure gas refrigerant compressed by thecompressor 3 flows through the discharge pipe 12 during both coolingoperation and heating operation. Low-temperature, low-pressurerefrigerant (gas refrigerant or two-phase refrigerant) that hasundergone evaporation flows through the suction pipe 11 during bothcooling operation and heating operation. The suction pipe 11 isconnected with a service port 14 b with flare coupling on thelow-pressure side, and the discharge pipe 12 is connected with a serviceport 14 c with flare coupling on the high-pressure side. The serviceports 14 b and 14 c are used to connect a pressure gauge to measureoperating pressure during a test run made at the time of installation orrepair of the air-conditioning apparatus.

The indoor heat exchanger 7 is accommodated in the indoor unit 1.Further, the indoor air-sending fan 7 f for supplying air to the indoorheat exchanger 7 is installed in the indoor unit 1. Rotating the indoorair-sending fan 7 f creates a flow of air that passes through the indoorheat exchanger 7. Depending on the type of the indoor unit 1, examplesof the indoor air-sending fan 7 f used include a centrifugal fan (forexample, a sirocco fan or a turbo fan), a cross-flow fan, a mixed flowfan, and an axial flow fan (for example, a propeller fan). Although theindoor air-sending fan 7 f in the present example is disposed upstreamof the indoor heat exchanger 7 in the direction of the flow of aircreated by the indoor air-sending fan 7 f, the indoor air-sending fan 7f may be disposed downstream of the indoor heat exchanger 7.

The indoor unit 1 is further provided with components such as a suctionair temperature sensor 91 that detects the temperature of indoor airsucked in from the indoor space, a heat exchanger inlet temperaturesensor 92 that detects the temperature of refrigerant at the location ofthe indoor heat exchanger 7 that becomes the inlet during coolingoperation (the outlet during heating operation), and a heat exchangertemperature sensor 93 that detects the temperature (evaporatingtemperature or condensing temperature) of the two-phase portion ofrefrigerant in the indoor heat exchanger 7. Further, the indoor unit 1is provided with a refrigerant detection unit 99 described later. Thesevarious sensors each output a detection signal to the control unit 30that controls the indoor unit 1 or the entire air-conditioningapparatus.

Among the refrigerant pipes of the indoor unit 1, an indoor pipe 9 a onthe gas side is provided with a coupling 15 a (for example, a flarecoupling) located at its connection with the extension pipe 10 a on thegas side, to connect the extension pipe 10 a. Further, among therefrigerant pipes of the indoor unit 1, an indoor pipe 9 b on the liquidside is provided with a coupling 15 b (for example, a flare coupling)located at its connection with the extension pipe 10 b on the liquidside, to connect the extension pipe 10 b.

The control unit 30 has a microcomputer including components such as aCPU, a ROM, a RAM, and an input-output port. The control unit 30 iscapable of mutually communicating data with an operating unit 26described later. The control unit 30 in the present example controls theoperation of the indoor unit 1 or the entire air-conditioning apparatusincluding the operation of the indoor air-sending fan 7 f, based onsignals such as an operational signal from the operating unit 26 anddetection signals from various sensors. The control unit 30 may beprovided inside the housing of the indoor unit 1, or may be providedinside the housing of the outdoor unit 2. Further, the control unit 30may include an outdoor-unit control unit disposed in the outdoor unit 2,and an indoor-unit control unit disposed in the indoor unit 1 andcapable of data communication with the outdoor-unit control unit,

Next, operation of the refrigeration cycle 40 of the air-conditioningapparatus will be described. First, cooling operation will be described.In FIG. 1, solid arrows indicate the flow of refrigerant in coolingoperation. In cooling operation, the refrigerant circuit is configuredso that the flow path of refrigerant is switched by the refrigerant flowswitching device 4 as indicated by the solid arrows, causinglow-temperature, low-pressure refrigerant to flow to the indoor heatexchanger 7.

High-temperature, high-pressure gas refrigerant discharged from thecompressor 3 first enters the outdoor heat exchanger 5 via therefrigerant flow switching device 4. In cooling operation, the outdoorheat exchanger 5 acts as a condenser. That is, in the outdoor heatexchanger 5, heat is exchanged between the refrigerant circulated in theoutdoor heat exchanger 5, and the air (outside air) sent by the outdoorair-sending fan 5 f, and the condensation heat of the refrigerant isrejected to the sent air. This operation causes the refrigerant enteringthe outdoor heat exchanger 5 to be condensed into high-pressure liquidrefrigerant. The high-pressure liquid refrigerant enters the pressurereducing device 6 where its pressure is reduced, causing the refrigerantto turn into low-pressure, two-phase refrigerant. The low-pressure,two-phase refrigerant enters the indoor heat exchanger 7 of the indoorunit 1 via the extension pipe 10 b. In cooling operation, the indoorheat exchanger 7 acts as an evaporator. That is, in the indoor heatexchanger 7, heat is exchanged between the refrigerant circulated in theindoor heat exchanger 7, and the air (indoor air) sent by the indoorair-sending fan 7 f, and the evaporation heat of the refrigerant isremoved from the sent air. This operation causes the refrigerantentering the indoor heat exchanger 7 to be evaporated into low-pressuregas refrigerant or two-phase refrigerant. The air sent by the indoorair-sending fan 7 f is cooled as the refrigerant removes heat. Thelow-pressure gas refrigerant or two-phase refrigerant evaporated in theindoor heat exchanger 7 is sucked into the compressor 3 via theextension pipe 10 a and the refrigerant flow switching device 4. Therefrigerant sucked into the compressor 3 is compressed intohigh-temperature, high-pressure gas refrigerant. The above cycle isrepeated in cooling operation.

Next, heating operation will be described. In FIG. 1, dotted arrowsindicate the flow of refrigerant in heating operation. In heatingoperation, the refrigerant circuit is configured so that the flow pathof refrigerant is switched by the refrigerant flow switching device 4 asindicated by the dotted arrows, causing high-temperature, high-pressurerefrigerant to flow to the indoor heat exchanger 7. In heatingoperation, the refrigerant flows in a direction opposite to that incooling operation, with the indoor heat exchanger 7 acting as acondenser. That is, in the indoor heat exchanger 7, heat is exchangedbetween the refrigerant circulated in the indoor heat exchanger 7, andthe air sent by the indoor air-sending fan 7 f, and the condensationheat of the refrigerant is rejected to the sent air. The air sent by theindoor air-sending fan 7 f is thus heated as the refrigerant rejectsheat.

FIG. 2 is a front view illustrating the exterior configuration of theindoor unit 1 of the air-conditioning apparatus according toEmbodiment 1. FIG. 3 is a front view illustrating the internal structureof the indoor unit 1 (with front panels removed). FIG. 4 is a side viewillustrating the internal structure of the indoor unit 1. The left-handside in FIG. 4 indicates the front side (indoor-space side) of theindoor unit 1. In Embodiment 1, the indoor unit 1 is illustrated to beof a floor-standing type installed on the floor surface of the indoorspace that is the air-conditioned space. As a general rule, the relativepositions of components (for example, their relative verticalarrangement) in the following description will be based on those whenthe indoor unit 1 is installed in a usable state.

As illustrated in FIGS. 2 to 4, the indoor unit 1 includes a housing 111with a vertically elongated rectangular parallelepiped shape. An airinlet 112 for sucking in the air of the indoor space is provided in alower part of the front face of the housing 111. The air inlet 112 inthe present example is located at a position below the verticallycentral part of the housing 111 and in the vicinity of the floorsurface. An air outlet 113 for blowing out the air sucked in through theair inlet 112 is provided in an upper part of the front face of thehousing 111, that is, at a position higher than the air inlet 112 (forexample, above the vertically central part of the housing 111). Theoperating unit 26 is provided at a position on the front face of thehousing 111 above the air inlet 112 and below the air outlet 113. Theoperating unit 26 is connected to the control unit 30 via acommunication line, allowing data to be mutually communicated betweenthe operating unit 26 and the control unit 30. As described above, theoperating unit 26 is operated by the user to perform functions such asstarting and ending the operation of the indoor unit 1 (air-conditioningapparatus), switching operation modes, and setting a preset temperatureand a preset air volume. The operating unit 26 may be provided withcomponents such as a display unit and a voice output unit to provideinformation to the user.

The housing 111 is in the form of a hollow box with a front openingprovided on the front face of the housing 111. The housing 111 includesa first front panel 114 a, a second front panel 114 b, and a third frontpanel 114 c that are detachably attached over the front opening. Each ofthe first front panel 114 a, the second front panel 114 b, and the thirdfront panel 114 c has a substantially rectangular, flat plate shape. Thefirst front panel 114 a is detachably attached over a lower part of thefront opening of the housing 111. The first front panel 114 a isprovided with the air inlet 112. The second front panel 114 b isdisposed above and adjacent to the first front panel 114 a, anddetachably attached over the vertically central part of the frontopening of the housing 111. The second front panel 114 b is providedwith the operating unit 26. The third front panel 114 c is disposedabove and adjacent to the second front panel 114 b, and detachablyattached over an upper part of the front opening of the housing 111. Thethird front panel 114 c is provided with the air outlet 113.

The internal space of the housing 111 is roughly divided into a space115 a serving as an air-sending part, and a space 115 b located abovethe space 115 a and serving as a heat exchange part. The space 115 a andthe space 115 b are partitioned off by a partition plate 20 with a flatshape that is disposed substantially horizontally. The partition plate20 is provided with at least an air passage opening 20 a serving as anair passage between the space 115 a and the space 115 b. The space 115 ais exposed to the front side when the first front panel 114 a isdetached from the housing 111, and the space 115 b is exposed to thefront side when the second front panel 114 b and the third front panel114 c are detached from the housing 111. That is, the partition plate 20is placed at substantially the same height as the height of the upperend of the first front panel 114 a (or the lower end of the second frontpanel 114 b).

The indoor air-sending fan 7 f is disposed in the space 115 a to createa flow of air that travels toward the air outlet 113 from the air inlet112. The indoor air-sending fan 7 f in the present example is a siroccofan including a motor (not illustrated), and an impeller 107 connectedto the output shaft of the motor and having a plurality of bladesarranged circumferentially at equal intervals. The rotating axis of theimpeller 107 (the output shaft of the motor) is disposed substantiallyin parallel to the direction of the depth of the housing 111. Theimpeller 107 of the indoor air-sending fan 7 f is covered by a fancasing 108 having a spiral shape. The fan casing 108 is formed, forexample, as a component separate from the housing 111. An air inletopening 108 b for sucking in the indoor air through the air inlet 112 isprovided in the vicinity of the center of the spiral of the fan casing108. The air inlet opening 108 b is located opposite to the air inlet112. Further, an air outlet opening 108 a for blowing out the air to besent is located in the direction of the tangent to the spiral of the fancasing 108. The air outlet opening 108 a is oriented upward, andconnected to the space 115 b via the air passage opening 20 a of thepartition plate 20. In other words, the air outlet opening 108 acommunicates with the space 115 b via the air passage opening 20 a. Theopen end of the air outlet opening 108 a and the open end of the airpassage opening 20 a may be directly connected with each other, or maybe indirectly connected with each other via a component such as a ductmember.

An electrical component box 25 for accommodating components such asvarious electrical components, a board, and a microcomputerconstituting, for example, the control unit 30 are provided in the space115 a.

The indoor heat exchanger 7 is disposed in an air passage 81 in thespace 115 b. A drain pan (not illustrated) is provided below the indoorheat exchanger 7 to receive water condensed on the surface of the indoorheat exchanger 7. The drain pan may be formed as a part of the partitionplate 20, or may be formed as a component separate from the partitionplate 20 and disposed on the partition plate 20.

The refrigerant detection unit 99 is disposed close to a lower part ofthe area in the vicinity of the air inlet opening 108 b. The refrigerantdetection unit 99 detects, for example, the concentration of refrigerantin the air around the refrigerant detection unit 99, and outputs theresulting detection signal to the control unit 30. The control unit 30determines whether refrigerant leaks based on the detection signal fromthe refrigerant detection unit 99.

In the indoor unit 1, refrigerant may leak at the brazed joints in theindoor heat exchanger 7, and the couplings 15 a and 15 b. Further, therefrigerant used in Embodiment 1 has a density greater than the densityof air under atmospheric pressure. Thus, the refrigerant detection unit99 according to Embodiment 1 is located at a position in the housing 111below the indoor heat exchanger 7 and the couplings 15 a and 15 b. Thisconfiguration ensures that the refrigerant detection unit 99 is able todetect leaked refrigerant at least when the indoor air-sending fan 7 fis stopped. Although the refrigerant detection unit 99 is disposed closeto a lower part of the area in the vicinity of the air inlet opening 108b in Embodiment 1, the refrigerant detection unit 99 may be placed at adifferent position.

FIG. 5 is a flowchart illustrating an example of a refrigerant leakdetection process executed by the control unit 30. This refrigerant leakdetection process is repeatedly executed at predetermined time intervalseither at all time, that is, both time when the air-conditioningapparatus is operating and time when the air-conditioning apparatus isstopped, or only at a time when the air-conditioning apparatus isstopped.

In step S1 illustrated in FIG. 5, the control unit 30 acquires, based ona detection signal from the refrigerant detection unit 99, informationon the concentration of refrigerant in the vicinity of the refrigerantdetection unit 99.

Next, in step S2, whether the concentration of refrigerant in thevicinity of the refrigerant detection unit 99 is equal to or higher thana preset threshold is determined. When the refrigerant concentration isdetermined to be equal to or higher than the threshold, the processproceeds to step S3. When the refrigerant concentration is determined tobe less than the threshold, the process is ended.

In step S3, the operation of the indoor air-sending fan 7 f is started.When the indoor air-sending fan 7 f is already operating, the operationis continued as it is. In step S3, components such as a display unit anda voice output unit provided in the operating unit 26 may be used toinform the user that refrigerant leaks.

As described above, in the refrigerant leak detection process, theoperation of the indoor air-sending fan 7 f is started when arefrigerant leak is detected (that is, when the refrigerantconcentration detected by the refrigerant detection unit 99 is equal toor higher than a threshold). As a result, the indoor air is sucked in tothe air inlet 112, and the sucked indoor air is blown out from the airoutlet 113. This operation allows the leaked refrigerant to be dispersedinto the indoor space, thus preventing locally increased refrigerantconcentrations in the indoor space.

FIG. 6 illustrates the state of an indoor space 120 after operation ofthe indoor air-sending fan 7 f is started through the process of step S3illustrated in FIG. 5. As illustrated in FIG. 6, the air outlet 113 islocated below the ceiling surface. Thus, the height Ho of the upper endof the air outlet 113 above the floor surface is lower than the heightHc of the ceiling surface above the floor surface (Ho<Hc). At this time,refrigerant leakage is assumed to still continues.

Embodiment 1 uses a refrigerant with a density greater than the densityof air under atmospheric pressure. Thus, leaked refrigerant gas 121 of arelatively high concentration accumulates on the floor surface in thevicinity of the indoor unit 1 in the indoor space 120. As the indoorair-sending fan 7 f is started to operate, the leaked refrigerant gas121 is sucked in to the air inlet 112 as a refrigerant-air mixture inwhich refrigerant and air are mixed together. The sucked refrigerant-airmixture is blown out into the indoor space 120 through the air outlet113 as indicated by thick arrows in FIG. 6. The direction in which therefrigerant-air mixture is blown out is, for example, horizontal. Thatis, while leakage of refrigerant continues, the following sequence ofoperations is repeated continuously: a refrigerant-air mixturecontaining a relatively high concentration of refrigerant is sucked into the air inlet 112, and then blown out into the indoor space 120 atthe height Ho through the air outlet 113.

The refrigerant contained in the refrigerant-air mixture blown out atthe height Ho has a density greater than the density of air underatmospheric pressure. Thus, almost no refrigerant is dispersed to thespace above the height Ho, and as the refrigerant flows downward, therefrigerant is dispersed to the lower space. Thus, while leakage ofrefrigerant continues, the leaked refrigerant is gradually dispersed toa lower space 120 a that is a space in the indoor space 120 located at aheight equal to or below the height Ho.

After leakage of refrigerant ends, the refrigerant-air mixture sucked into the air inlet 112 gradually decreases in refrigerant concentration,and the refrigerant-air mixture blown out from the air outlet 113 alsogradually decreases in refrigerant concentration. This operation reducesthe difference between the density of the refrigerant-air mixture blownout at the height Ho, and the density of air. As a result, therefrigerant contained in the refrigerant-air mixture also begins to bedispersed to the space above the height Ho. That is, after leakage ofrefrigerant ends, the refrigerant is gradually dispersed also to anupper space 120 b that is a space in the indoor space 120 located abovethe height Ho and below the height Hc.

Hereinafter, the above-mentioned phenomenon will be described morespecifically with reference to experimental results.

FIG. 7 is a plan view illustrating the configuration of the indoor space120 used in an experiment. As illustrated in FIG. 7, the indoor space120 is an enclosed space whose planar shape is a square of 4 m×4 m. Theheight Hc of the ceiling surface of the indoor space 120 is 2.5 m. Thatis, the indoor space 120 has a volume of 40 m³. The indoor unit 1 isdisposed on the floor surface along the laterally central part of onewall surface in the indoor space 120. The height Ho of the air outlet113 of the indoor unit 1 is 1.5 m. R-32 is used as the refrigerant. Thelower flammable limit (LFL) of R-32 is 0.306 kg/m³ (=14.4 vol %). Theindoor air-sending fan 7 f is set to start operating when theconcentration of refrigerant detected by the refrigerant detection unit99 in the indoor unit 1 (in the housing 111) increases to 3.6 vol %(that is, ¼ the LFL).

Four refrigerant concentration sensors 122 a, 122 b, 122 c, and 122 dused for refrigerant concentration measurement are disposed at differentheights in the central part of the indoor space 120. The refrigerantconcentration sensors 122 a, 122 b, 122 c, and 122 d are respectivelylocated at heights of 0.5 m, 1.0 m, 1.5 m, and 2.0 m above the floorsurface. That is, the refrigerant concentration sensors 122 a, 122 b,and 122 c measure the concentrations of refrigerant in the lower space120 a located at a height equal to or below the height Ho. Of thesesensors, the refrigerant concentration sensor 122 c measures theconcentration of refrigerant at the same height as the height Ho of theair outlet 113. The refrigerant concentration sensor 122 d measures theconcentration of refrigerant at a height in the upper space 120 b abovethe height Ho.

In a first experiment, refrigerant was leaked at a leak rate of 10 kg/hin the housing 111 of the indoor unit 1, and the concentration of therefrigerant was measured by each of the four refrigerant concentrationsensors 122 a, 122 b, 122 c, and 122 d. The total amount of refrigerantleaked was set to 12.24 kg. This total amount of refrigerant correspondsto the LFL for the volume of the indoor space 120. That is, the totalamount of refrigerant is set so that the concentration of refrigerantreaches the LFL when the refrigerant is dispersed uniformly throughoutthe entire indoor space 120.

FIG. 8 is a graph illustrating changes in refrigerant concentration overtime in the first experiment. The horizontal axis of the graphrepresents time elapsed [minute] since the start of refrigerant leakage,and the vertical axis represents refrigerant (R-32) concentration [vol%]. The thin solid curved line in the graph represents changes inrefrigerant concentration measured at a height of 0.5 m by therefrigerant concentration sensor 122 a. The thin dashed curved linerepresents changes in refrigerant concentration measured at a height of1.0 m by the refrigerant concentration sensor 122 b. The thick solidcurved line represents changes in refrigerant concentration measured ata height of 1.5 m by the refrigerant concentration sensor 122 c. Thethick dashed curved line represents changes in refrigerant concentrationmeasured at a height of 2.0 m by the refrigerant concentration sensor122 d.

As illustrated in FIG. 8, the refrigerant concentrations measured by therefrigerant concentration sensors 122 a, 122 b, and 122 c increasemonotonously over time generally in the time period between the startand end of refrigerant leakage (between the 0th minute and approximatelythe 75th minute), and eventually exceeds the LFL. Then, after the end ofrefrigerant leakage, these refrigerant concentrations graduallydecrease, eventually approaching the LFL. These refrigerantconcentrations are above the LFL in a time period T1 betweenapproximately the 60th minute and approximately the 130th minute of theelapsed time. This result indicates that a flammable concentrationregion is formed in the lower space 120 a in the time period T1. Therefrigerant concentrations measured by the refrigerant concentrationsensors 122 a, 122 b, and 122 c exhibit substantially identical valuesirrespective of the elapsed time. This result indicates substantiallyuniform dispersion of leaked refrigerant in the lower space 120 a.

Meanwhile, the refrigerant concentration measured by the refrigerantconcentration sensor 122 d remains substantially 0 vol % in the timeperiod between the start and end of refrigerant leakage. Although thisrefrigerant concentration starts to increase after the end ofrefrigerant leakage, the refrigerant concentration never exceeds theLFL, and eventually approaches the LFL. This result indicates thatalmost no refrigerant disperses to the upper space 120 b until the endof refrigerant leakage, and such dispersion begins after the end ofrefrigerant leakage.

In a second experiment, the total amount of refrigerant was set to 6.12kg (half of that in the first experiment). FIG. 9 is a graphillustrating changes in refrigerant concentration over time in thesecond experiment. As illustrated in FIG. 9, the changes in refrigerantconcentration in the second experiment exhibit a tendency similar tothat of the first experiment.

As in the first experiment, the refrigerant concentrations measured bythe refrigerant concentration sensors 122 a, 122 b, and 122 c increasemonotonously over time generally in the time period between the startand end of refrigerant leakage (between the 0th minute and approximatelythe 35th minute), but does not reach the LFL. Then, after the end ofrefrigerant leakage, these refrigerant concentrations graduallydecrease, eventually approaching 7.2 vol % (½ of the LFL). Due to thesmall total amount of refrigerant in the second experiment, no timeperiod existed in which the refrigerant concentration exceeds the LFL.

As in the first experiment, the refrigerant concentration measured bythe refrigerant concentration sensor 122 d remains substantially 0 vol %in the time period between the start and end of refrigerant leakage.This refrigerant concentration starts to increase after the end ofrefrigerant leakage, eventually approaching 7.2 vol % (½ of the LFL).

The following findings can be derived from the phenomenon describedabove with reference to FIG. 6, and the experimental results describedabove with reference to FIGS. 7 to 9.

(1) When the total amount of refrigerant is set equal to or greater thanthe amount corresponding to the LFL for the entire volume of the indoorspace 120, a flammable concentration region may be formed in the lowerspace 120 a.

(2) To prevent formation of a flammable concentration region in thelower space 120 a, the total amount of refrigerant needs to be set lessthan the amount corresponding to the LFL for the volume of the lowerspace 120 a.

The entire volume of the indoor space 120 is expressed by the product ofthe floor area of the indoor space 120, and the height Hc of the ceilingsurface above the floor surface of the indoor space 120. The volume ofthe lower space 120 a is expressed by the product of the floor area ofthe indoor space 120, and the height Ho at which the air outlet 113 islocated above the floor surface of the indoor space 120 in a state inwhich the indoor unit 1 is placed in the indoor space 120. Values suchas the floor area of the indoor space 120, the height Hc of the ceilingsurface, and the height Ho of the air outlet 113 can not only bedetermined by the actual dimensions of the indoor space 120 in which theindoor unit 1 is actually placed but can also be determined or estimatedfrom the specifications of the air-conditioning apparatus or the indoorunit 1 (catalog specifications).

For example, the floor area can be determined by the applicable floorarea specified by the specifications of the air-conditioning apparatusor the indoor unit 1.

The applicable floor area specified by the specifications of theair-conditioning apparatus or the indoor unit 1 is written in documentssuch as the catalog, installation manual, and delivery specificationssheet of the air-conditioning apparatus by using expressions such as“Approximate Air-conditioned Area” and “Approximate Room Size”.Alternatively, the applicable floor area specified by the specificationsof the air-conditioning apparatus or the indoor unit 1 can be determinedby dividing the cooling capacity or heating capacity of theair-conditioning apparatus including the indoor unit 1 and the outdoorunit 2 by the cooling load or heating load used as a calculationcriterion. The cooling capacity or heating capacity is written in, forexample, the nameplate, catalog, or delivery specifications sheet of theindoor unit 1 or the outdoor unit 2 as rated capacity or maximumcapacity. If both rated capacity and maximum capacity are written,maximum capacity is used. The cooling load or heating load used as thecalculation criterion is written in the catalog, the installationmanual, the delivery specifications sheet, or other documents.

FIG. 13 illustrates an example of items written in the catalog. Asillustrated in FIG. 13, if, for example, the maximum cooling capacity ofthe air-conditioning apparatus is 5.0 kW, and the cooling load used asthe calculation criterion for the indoor space in which the indoor unit1 is installed is in the range of 170 W/m² to 115 W/m² (the cooling loadused as the calculation criterion for general offices is used as anexample here), the applicable floor area is determined to be in therange of 29 m² to 43 m².

When the indoor unit 1 is of a floor-standing type, the indoor unit 1 isinstalled on the floor surface. Thus, for the indoor unit 1 of afloor-standing type, the height Ho of the air outlet 113 above the floorsurface corresponds to the height dimension of the indoor unit 1 fromits bottom surface (for example, the surface in contact with the floorsurface) to the air outlet 113. The height dimension of the indoor unit1 from the bottom surface to the air outlet 113 can be determined basedon the dimensions of various parts of the indoor unit 1 written in thecatalog, the delivery specifications sheet, or other documents.Alternatively, the height dimension of the indoor unit 1 from the bottomsurface to the air outlet 113 can be also determined by actualmeasurement.

When the indoor unit 1 used is of a type (for example, a wall-mountedtype) other than a floor-standing type, the indoor unit 1 is installedat a predetermined installation height above the floor surface. Thus,the height Ho of the air outlet 113 of the indoor unit 1 above the floorsurface can be determined by the sum of the height dimension of theindoor unit 1 from the bottom surface to the air outlet 113, and theinstallation height of the indoor unit 1 above the floor surface (thatis, the height dimension from the floor surface to the bottom surface ofthe indoor unit 1). The height dimension of the indoor unit 1 from thebottom surface to the air outlet 113 can be determined based on thedimensions of various parts of the indoor unit 1 written in the catalog,the delivery specifications sheet, or other documents. Alternatively,the height dimension of the indoor unit 1 from the bottom surface to theair outlet 113 can be also determined by actual measurement. Theinstallation height of the indoor unit 1 above the floor surface iswritten in the catalog, the installation manual, the deliveryspecifications sheet, or other documents. For example, if the heightdimension of the indoor unit 1 from the bottom surface to the air outlet113 is 10 cm, and the installation height of the indoor unit 1 above thefloor surface is 180 cm, the height Ho of the air outlet 113 above thefloor surface is determined to be 190 cm.

The lower flammable limit LFL can be determined by the type ofrefrigerant. The type of refrigerant is written in, for example, thenameplate of the outdoor unit 2, the catalog, the installation manual,or the delivery specifications sheet. The lower flammable limit LFL foreach individual type of refrigerant is written in literature such as theinternational standard IEC 60335-2-40.

The amount of refrigerant charge, M, can be determined by the sum ofrefrigerant charged at the factory, and the amount of refrigerant addedon-site as needed depending on the length of refrigerant pipes. Theamount of refrigerant charged at the factory is written in, for example,the nameplate of the outdoor unit 2, the catalog, the installationmanual, or the delivery specifications sheet. The amount of refrigerantadded on-site depending on the length of refrigerant pipes is written inthe catalog, the installation manual, or other documents.

FIG. 14 illustrates an example of items written in the catalog or theinstallation manual. In the example illustrated in FIG. 14, such itemsinclude the type of refrigerant, the amount of refrigerant charge atfactory, and the amount of refrigerant added for refrigerant pipelengths over 30 m.

The catalog and the delivery specifications sheet, which are documentsused during business negotiations, are distributed to the public and canbe also obtained from websites. Further, the installation manual ispackaged with at least one of the indoor unit 1 and the outdoor unit 2,and can be also obtained from websites. The nameplate is attached on theindoor unit 1 and the outdoor unit 2.

As described above, the air-conditioning apparatus according toEmbodiment 1 includes the refrigeration cycle 40 through whichrefrigerant is circulated, the indoor unit 1 that accommodates at leastthe indoor heat exchanger 7 of the refrigeration cycle 40, the indoorunit 1 being disposed in the indoor space 120, and the control unit 30that controls the indoor unit 1. The refrigerant is a flammablerefrigerant with a density greater than the density of air underatmospheric pressure. The indoor unit 1 includes the indoor air-sendingfan 7 f, the air inlet 112 through which the air of the indoor space 120is sucked in, and the air outlet 113 located above the air inlet 112 andthrough which the air sucked in through the air inlet 112 is blown outto the indoor space 120. The air outlet 113 is provided on the frontface or the side face (the front face in the present example) of thehousing 111 of the indoor unit 1. The control unit 30 activates theindoor air-sending fan 7 f when leakage of the refrigerant is detected.When M [kg] represents the amount of charge of the refrigerant in therefrigeration cycle 40, LFL [kg/m³] represents the lower flammable limitof the refrigerant, A [m²] represents the floor area of the indoor space120, and Ho [m] represents the height of the air outlet 113 above thefloor surface of the indoor space 120, the amount of charge M, the lowerflammable limit LFL, the floor area A, and the height Ho satisfy therelationship of M<LFL×A×Ho.

This configuration ensures that even if the entire amount of refrigerantcharged in the refrigeration cycle 40 leaks to the indoor space 120, therefrigerant concentration in the lower space 120 a does not increase tothe LFL. Consequently, formation of a flammable concentration region inthe indoor space 120 can be reduced.

For the air-conditioning apparatus according to Embodiment 1, the floorarea mentioned above may be the applicable floor area specified by thespecifications of the air-conditioning apparatus or the indoor unit 1.

Both to reduce formation of a flammable concentration region and toensure sufficient air-conditioning capacity of the air-conditioningapparatus to the indoor space 120, the amount of charge M, the lowerflammable limit LFL, the floor area A, and the height Ho may be made tosatisfy the relationship of S×LFL×A×Ho≦M<LFL×A×Ho, where S denotes acoefficient greater than 0 and less than 1 (0<S<1). The coefficient S isa value that varies with factors such as the range of air conditions(for example, the range of outside air temperatures) set in advance inimplementing the air-conditioning apparatus, the maximum length of theextension pipe, the specifications of the heat exchanger used in theair-conditioning apparatus, and the type of refrigerant. Depending onthe case, the coefficient S may have a value of about 1/10, or may havea value of about 1/100 or less.

Embodiment 2

An air-conditioning apparatus according to Embodiment 2 of the presentinvention will be described. In the air-conditioning apparatus accordingto Embodiment 2, the amount of refrigerant charge M, the lower flammablelimit LFL of the refrigerant, the floor area A of the indoor space 120,and the height Ho of the air outlet 113 satisfy the relationship ofM≧LFL×A×Ho.

FIG. 10 is a cross-sectional view illustrating the configuration in thevicinity area of the air outlet 113 of the indoor unit 1 of theair-conditioning apparatus according to Embodiment 2. The configurationof the indoor unit 1 in areas other than the vicinity of the air outlet113 is the same as that of the indoor unit 1 according to Embodiment 1,thus illustration and description of the configuration in these areaswill be omitted.

As illustrated in FIG. 10, the indoor unit 1 according to Embodiment 2has, at the air outlet 113, a single or a plurality of (five in thepresent example) vertical air deflector vanes 123. The vertical airdeflector vanes 123 are capable of rotating about the rotation axisprovided in the horizontal direction, between an angular positionoriented diagonally downward as indicated by dashed lines in FIG. 10 andan angular position oriented diagonally upward as indicated by solidlines in FIG. 10. With the vertical air deflector vanes 123 set in thedownward angular position, air is blown out downward from the air outlet113. With the vertical air deflector vanes 123 set in the upward angularposition, air is blown out upward (as indicated by arrows in FIG. 10)from the air outlet 113. The vertical air deflector vanes 123 arecontrolled by the control unit 30 so that the vertical air deflectorvanes 123 are driven to rotate by a drive mechanism (not illustrated).

FIG. 11 is a flowchart illustrating an example of a refrigerant leakdetection process executed by the control unit 30. This refrigerant leakdetection process is repeatedly executed at predetermined time intervalsat all time, that is, both time when the air-conditioning apparatus isoperating and time when the air-conditioning apparatus is stopped, oronly at a time when the air-conditioning apparatus is stopped. Step S11to S13 are the same as steps S1 to S3 illustrated in FIG. 5.

As illustrated in FIG. 11, when the concentration of refrigerant isdetermined to be equal to or higher than a threshold, step S14 isexecuted in addition to S13 that is the same as S3. At step S14, thevertical air deflector vanes 123 are set to be oriented more upward thanthe horizontal plane. The ideal angle of the vertical air deflectorvanes 123 at this time is 45 degrees to the horizontal plane. This idealangle causes air to be blown out upward (toward the upper space 120 b)from the air outlet 113. Step S13 may be executed after S14 is executed.

FIG. 12 illustrates the state of the indoor space 120 after the verticalair deflector vanes 123 are set to be oriented upward through theprocess of step S14. As illustrated in FIG. 12, a refrigerant-airmixture is blown out upward from the air outlet 113. Thus, unlike thearrangement illustrated in FIG. 6, the refrigerant can be dispersedthroughout the entire indoor space 120 including the upper space 120 bfrom immediately after the start of refrigerant leakage. Consequently,Embodiment 2 reduces formation of a flammable concentration region inthe indoor space 120 even when the amount of refrigerant charge is setequal to or greater than the amount corresponding to the LFL for thevolume of the lower space 120 a. The amount of refrigerant charge ispreferable to be set less than the amount corresponding to the LFL forthe entire volume of the indoor space 120.

As described above, the air-conditioning apparatus according toEmbodiment 1 includes the refrigeration cycle 40 through whichrefrigerant is circulated, the indoor unit 1 that accommodates at leastthe indoor heat exchanger 7 of the refrigeration cycle 40, the indoorunit 1 being disposed in the indoor space 120, and the control unit 30that controls the indoor unit 1. The refrigerant is a flammablerefrigerant with a density greater than the density of air underatmospheric pressure. The indoor unit 1 includes the indoor air-sendingfan 7 f, the air inlet 112 through which the air of the indoor space 120is sucked in, the air outlet 113 located above the air inlet 112 andthrough which the air sucked in through the air inlet 112 is blown outto the indoor space 120, and the vertical air deflector vanes 123located at the air outlet 113. The air outlet 113 is provided on thefront face or the side face of the housing 111 of the indoor unit 1.When M [kg] represents the amount of charge of the refrigerant in therefrigeration cycle 40, LFL [kg/m³] represents the lower flammable limitof the refrigerant, A [m²] represents the floor area of the indoor space120, and Ho [m] represents the height of the air outlet 113 above thefloor surface of the indoor space 120, the amount of charge M, the lowerflammable limit LFL, the floor area A, and the height Ho satisfy therelationship of M≧LFL×A×Ho. The control unit 30 activates the indoorair-sending fan 7 f and sets the vertical air deflector vanes 123 to anupward orientation when leakage of the refrigerant is detected.

This configuration allows leaked refrigerant to be dispersed not only tothe lower space 120 a but also to the upper space 120 b. Consequently,formation of a flammable concentration region in the indoor space 120can be reduced even when the amount of refrigerant charge is set equalto or greater than the amount corresponding to the LFL for the volume ofthe lower space 120 a.

Further, in the air-conditioning apparatus according to Embodiment 2,when Hc [m] represents the height of the ceiling surface above the floorsurface of the indoor space 120, the amount of charge M, the lowerflammable limit LFL, the floor area A, and the height Hc may satisfy therelationship of M<LFL×A×Hc.

This configuration reduces formation of a flammable concentration regionin the indoor space 120 even if the entire amount of refrigerant chargedin the refrigeration cycle 40 leaks to the indoor space 120.

In the air-conditioning apparatus according to Embodiment 2, the floorarea mentioned above may be the applicable floor area specified by thespecifications of the air-conditioning apparatus or the indoor unit 1.

Other Embodiments

The present invention is not limited to the above embodiments butcapable of various modifications.

For example, although the air outlet 113 and the air inlet 112 areprovided on the front face of the housing 111 of the indoor unit 1 inthe embodiments mentioned above, the air outlet 113 and the air inlet112 may be provided on the side face of the housing 111.

Although the above-mentioned embodiments are directed to the indoor unit1 that is of a floor-standing type, the present invention is alsoapplicable to any other type of indoor unit (for example, a wall-mountedindoor unit) placed so that the height Ho of the air outlet is lowerthan the height Hc of the ceiling surface.

REFERENCE SIGNS LIST

indoor unit 2 outdoor unit 3 compressor 4 refrigerant flow switchingdevice 5 outdoor heat exchanger 5 f outdoor air-sending fan 6 pressurereducing device 7 indoor heat exchanger 7 f indoor air-sending fan 9 a,9 b indoor pipe 10 a, 10 b extension pipe 11 suction pipe 12 dischargepipe 13 a, 13 b extension-pipe connection valve 14 a, 14 b, 14 c serviceport 15 a, 15 b coupling 20 partition plate 20 a air passage opening 25electrical component box 26 operating unit 30 control unit 40refrigeration cycle 81 air passage 91 suction air temperature sensor 92heat exchanger inlet temperature sensor 93 heat exchanger temperaturesensor 99 refrigerant detection unit 107 impeller 108 fan casing 108 aair outlet opening 108 b air inlet opening 111 housing 112 air inlet 113air outlet 114 a first front panel 114 b second front panel 114 c thirdfront panel 115 a, 115 b space 120 indoor space 120 a lower space 120 bupper space 121 leaked refrigerant gas 122 a, 122 b, 122 c, 122 drefrigerant concentration sensor 123 vertical air deflector vane

1. An air-conditioning apparatus comprising: a refrigeration cyclethrough which refrigerant is circulated; and an indoor unitaccommodating at least an indoor heat exchanger of the refrigerationcycle, the indoor unit being disposed in an indoor space the refrigerantbeing a flammable refrigerant with a density greater than a density ofair under atmospheric pressure, the indoor unit including an air-sendingfan, an air inlet through which air of the indoor space is sucked in,and an air outlet through which the air sucked in through the air inletis blown out to the indoor space, the air-conditioning apparatus beingconfigured to dilute leaked refrigerant by operation of the air-sendingfan, when M [kg] represents an amount of charge of the refrigerant inthe refrigeration cycle, LFL [kg/m³] represents a lower flammable limitof the refrigerant, A [m²] represents a floor area of the indoor space,and Ho [m] represents a height of the air outlet above a floor surfaceof the indoor space, the amount of charge M, the lower flammable limitLFL, the floor area A, and the height Ho satisfying a relationship ofM<LFL×A×Ho.
 2. An air-conditioning apparatus comprising: a refrigerationcycle through which refrigerant is circulated; and an indoor unitaccommodating at least an indoor heat exchanger of the refrigerationcycle, the indoor unit being disposed in an indoor space; and therefrigerant being a flammable refrigerant with a density greater than adensity of air under atmospheric pressure, the indoor unit including anair-sending fan, an air inlet through which air of the indoor space issucked in, an air outlet through which the air sucked in through the airinlet is blown out to the indoor space, and a vertical air deflectorvane located at the air outlet, the air-conditioning apparatus beingconfigured to dilute leaked refrigerant by operation of the air-sendingfan and to blow out the air upward through the air outlet by thevertical air deflector vane, when M [kg] represents an amount of chargeof the refrigerant in the refrigeration cycle, LFL [kg/m³] represents alower flammable limit of the refrigerant, A [m²] represents a floor areaof the indoor space, Ho [m] represents a height of the air outlet abovea floor surface of the indoor space, and Hc [m] represents a height of aceiling surface above the floor surface of the indoor space, the amountof charge M, the lower flammable limit LFL, the floor area A, the heightHo, and the height Hc satisfying a relationship of LFL×A×Ho≦M<LFL×A×Hc.3. (canceled)
 4. The air-conditioning apparatus of claim 1, wherein thefloor area is a floor area specified by specifications of theair-conditioning apparatus or the indoor unit.
 5. The air-conditioningapparatus of claim 1, further comprising a control unit configured tocontrol the indoor unit, wherein the control unit is configured toactivate the air-sending fan when leakage of the refrigerant isdetected.
 6. The air-conditioning apparatus of claim 5, wherein theindoor unit includes a refrigerant detection unit, and the control unitis configured to activate the air-sending fan by a time whenconcentration of the refrigerant detected by the refrigerant detectionunit reaches ¼ of the lower flammable limit.
 7. The air-conditioningapparatus of claim 1, wherein the indoor unit includes a refrigerantdetection unit, the indoor heat exchanger is connected to an extensionpipe via a coupling, and the refrigerant detection unit is provided in ahousing of the indoor unit and below the indoor heat exchanger and thecoupling.
 8. The air-conditioning apparatus of claim 1, wherein adirection in which the air is blown out through the air outlet is ahorizontal direction.
 9. The air-conditioning apparatus of claim 2,wherein the floor area is a floor area specified by specifications ofthe air-conditioning apparatus or the indoor unit.
 10. Theair-conditioning apparatus of claim 2, further comprising a control unitconfigured to control the indoor unit, wherein the control unit isconfigured to activate the air-sending fan and set the vertical airdeflector vane to an upward orientation when leakage of the refrigerantis detected.
 11. A refrigerant amount setting method of anair-conditioning apparatus, the air-conditioning apparatus including arefrigeration cycle through which refrigerant is circulated, and anindoor unit accommodating at least an indoor heat exchanger of therefrigeration cycle, the indoor unit being disposed in an indoor space,the refrigerant being a flammable refrigerant with a density greaterthan a density of air under atmospheric pressure, the indoor unitincluding an air-sending fan, an air inlet through which air of theindoor space is sucked in, and an air outlet through which the airsucked in through the air inlet is blown out to the indoor space, theair-conditioning apparatus being configured to dilute leaked refrigerantby operation of the air-sending fan, the refrigerant amount settingmethod of the air-conditioning apparatus comprising setting an amount ofthe refrigerant of the air-conditioning apparatus, the settingincluding, when M [kg] represents an amount of charge of the refrigerantin the refrigeration cycle, LFL [kg/m³] represents a lower flammablelimit of the refrigerant, A [m²] represents a floor area of the indoorspace, and Ho [m] represents a height of the air outlet above a floorsurface of the indoor space, setting the amount of charge M so that theamount of charge M, the lower flammable limit LFL, the floor area A, andthe height Ho satisfy a relationship of M<LFL×A×Ho.
 12. The refrigerantamount setting method of an air-conditioning apparatus of claim 11,wherein the floor area is a floor area specified by specifications ofthe air-conditioning apparatus or the indoor unit.
 13. A refrigerantamount setting method of an air-conditioning apparatus, theair-conditioning apparatus including a refrigeration cycle through whichrefrigerant is circulated, and an indoor unit accommodating at least anindoor heat exchanger of the refrigeration cycle, the indoor unit beingdisposed in an indoor space, the refrigerant being a flammablerefrigerant with a density greater than a density of air underatmospheric pressure, the indoor unit including an air-sending fan, anair inlet through which air of the indoor space is sucked in, an airoutlet through which the air sucked in through the air inlet is blownout to the indoor space, and a vertical air deflector vane located atthe air outlet, the air-conditioning apparatus being configured todilute leaked refrigerant by operation of the air-sending fan and toblow out the air upward through the air outlet by the vertical airdeflector vane, the refrigerant amount setting method of theair-conditioning apparatus comprising setting an amount of therefrigerant of the air-conditioning apparatus, the setting including,when M [kg] represents an amount of charge of the refrigerant in therefrigeration cycle, LFL [kg/m³] represents a lower flammable limit ofthe refrigerant, A [m²] represents a floor area of the indoor space, Ho[m] represents a height of the air outlet above a floor surface of theindoor space, and Hc [m] represents a height of a ceiling surface abovethe floor surface of the indoor space, setting the amount of charge M sothat the amount of charge M, the lower flammable limit LFL, the floorarea A, the height Ho, and the height Hc satisfy a relationship ofLFL×A×Ho≦M<LFL×A×Hc.
 14. The refrigerant amount setting method of anair-conditioning apparatus of claim 13, wherein the floor area is afloor area specified by specifications of the air-conditioning apparatusor the indoor unit.